Add local_data and is_local to raft_entry

src/leader.c

@@ -224,7 +224,11 @@ static void leaderMaybeCheckpointLegacy(struct leader *l)
  tracef("raft_malloc - no mem");
  goto err_after_buf_alloc;
  }
+#ifdef USE_SYSTEM_RAFT
  rv = raft_apply(l->raft, apply, &buf, 1, leaderCheckpointApplyCb);
+#else
+ rv = raft_apply(l->raft, apply, &buf, NULL, 1, leaderCheckpointApplyCb);
+#endif
  if (rv != 0) {
  tracef("raft_apply failed %d", rv);
  raft_free(apply);
@@ -332,7 +336,13 @@ static int leaderApplyFrames(struct exec *req,
  apply->type = COMMAND_FRAMES;
  idSet(apply->req.req_id, req->id);
 
+#ifdef USE_SYSTEM_RAFT
  rv = raft_apply(l->raft, &apply->req, &buf, 1, leaderApplyFramesCb);
+#else
+ /* TODO actual WAL slice goes here */
+ struct raft_entry_local_data local_data = {};
+ rv = raft_apply(l->raft, &apply->req, &buf, &local_data, 1, leaderApplyFramesCb);
+#endif
  if (rv != 0) {
  tracef("raft apply failed %d", rv);
  goto err_after_command_encode;

src/raft.h

@@ -197,6 +197,28 @@ enum {
  RAFT_CHANGE /* Raft configuration change. */
 };
 
+/**
+ * A small fixed-size inline buffer that stores extra data for a raft_entry
+ * that is different for each node in the cluster.
+ *
+ * A leader initializes the local data for an entry before passing it into
+ * raft_apply. This local data is stored in the volatile raft log and also
+ * in the persistent raft log on the leader. AppendEntries messages sent by
+ * the leader never contain the local data for entries.
+ *
+ * When a follower accepts an AppendEntries request, it invokes a callback
+ * provided by the FSM to fill out the local data for each new entry before
+ * appending the entries to its log (volatile and persistent). This local
+ * data doesn't have to be the same as the local data that the leader computed.
+ *
+ * When starting up, a raft node reads the local data for each entry for its
+ * persistent log as part of populating the volatile log.
+ */
+struct raft_entry_local_data {
+ /* Must be the only member of this struct. */
+ uint8_t buf[16];
+};
+
 /**
  * A single entry in the raft log.
  *
@@ -220,12 +242,27 @@ enum {
  *
  * This arrangement makes it possible to minimize the amount of memory-copying
  * when performing I/O.
+ *
+ * The @is_local field is set to `true` by a leader that appends an entry to its
+ * volatile log. It is set to `false` by a follower that copies an entry received
+ * via AppendEntries to its volatile log. It is not represented in the AppendEntries
+ * message or in the persistent log. This field can be used by the FSM's `apply`
+ * callback to handle a COMMAND entry differently depending on whether it
+ * originated locally.
+ *
+ * Note: The @local_data and @is_local fields do not exist when we use an external
+ * libraft, because the last separate release of libraft predates their addition.
+ * The ifdef at the very top of this file ensures that we use the system raft headers
+ * when we build against an external libraft, so there will be no ABI mismatch as
+ * a result of incompatible struct layouts.
  */
 struct raft_entry
 {
- raft_term term; /* Term in which the entry was created. */
- unsigned short type; /* Type (FSM command, barrier, config change). */
+ raft_term term; /* Term in which the entry was created. */
+ unsigned short type; /* Type (FSM command, barrier, config change). */
+ bool is_local; /* Placed here so it goes in the padding after @type. */
  struct raft_buffer buf; /* Entry data. */
+ struct raft_entry_local_data local_data;
  void *batch; /* Batch that buf's memory points to, if any. */
 };
 
@@ -1082,6 +1119,7 @@ struct raft_apply
 RAFT_API int raft_apply(struct raft *r,
  struct raft_apply *req,
  const struct raft_buffer bufs[],
+ const struct raft_entry_local_data local_data[],
  const unsigned n,
  raft_apply_cb cb);
 

src/raft/client.c

@@ -14,6 +14,7 @@
 int raft_apply(struct raft *r,
  struct raft_apply *req,
  const struct raft_buffer bufs[],
+ const struct raft_entry_local_data local_data[],
  const unsigned n,
  raft_apply_cb cb)
 {
@@ -41,7 +42,7 @@ int raft_apply(struct raft *r,
  req->cb = cb;
 
  /* Append the new entries to the log. */
- rv = logAppendCommands(r->log, r->current_term, bufs, n);
+ rv = logAppendCommands(r->log, r->current_term, bufs, local_data, n);
  if (rv != 0) {
  goto err;
  }
@@ -90,7 +91,7 @@ int raft_barrier(struct raft *r, struct raft_barrier *req, raft_barrier_cb cb)
  req->index = index;
  req->cb = cb;
 
- rv = logAppend(r->log, r->current_term, RAFT_BARRIER, &buf, NULL);
+ rv = logAppend(r->log, r->current_term, RAFT_BARRIER, buf, (struct raft_entry_local_data){}, true, NULL);
  if (rv != 0) {
  goto err_after_buf_alloc;
  }

src/raft/fixture.c

@@ -1316,7 +1316,8 @@ static void copyLeaderLog(struct raft_fixture *f)
  buf.base = raft_malloc(buf.len);
  assert(buf.base != NULL);
  memcpy(buf.base, entry->buf.base, buf.len);
- rv = logAppend(f->log, entry->term, entry->type, &buf, NULL);
+ /* FIXME(cole) what to do here for is_local? */
+ rv = logAppend(f->log, entry->term, entry->type, buf, (struct raft_entry_local_data){}, false, NULL);
  assert(rv == 0);
  }
  logRelease(raft->log, 1, entries, n);

src/raft/log.c

@@ -545,7 +545,9 @@ int logReinstate(struct raft_log *l,
 int logAppend(struct raft_log *l,
  const raft_term term,
  const unsigned short type,
- const struct raft_buffer *buf,
+ struct raft_buffer buf,
+ struct raft_entry_local_data local_data,
+ bool is_local,
  void *batch)
 {
  int rv;
@@ -556,7 +558,6 @@ int logAppend(struct raft_log *l,
  assert(term > 0);
  assert(type == RAFT_CHANGE || type == RAFT_BARRIER ||
  type == RAFT_COMMAND);
- assert(buf != NULL);
 
  rv = ensureCapacity(l);
  if (rv != 0) {
@@ -565,16 +566,18 @@ int logAppend(struct raft_log *l,
 
  index = logLastIndex(l) + 1;
 
- rv = refsInit(l, term, index, *buf, batch);
+ rv = refsInit(l, term, index, buf, batch);
  if (rv != 0) {
  return rv;
  }
 
  entry = &l->entries[l->back];
  entry->term = term;
  entry->type = type;
- entry->buf = *buf;
+ entry->buf = buf;
  entry->batch = batch;
+ entry->local_data = local_data;
+ entry->is_local = is_local;
 
  l->back += 1;
  l->back = l->back % l->size;
@@ -585,6 +588,7 @@ int logAppend(struct raft_log *l,
 int logAppendCommands(struct raft_log *l,
  const raft_term term,
  const struct raft_buffer bufs[],
+ const struct raft_entry_local_data local_data[],
  const unsigned n)
 {
  unsigned i;
@@ -596,8 +600,8 @@ int logAppendCommands(struct raft_log *l,
  assert(n > 0);
 
  for (i = 0; i < n; i++) {
- const struct raft_buffer *buf = &bufs[i];
- rv = logAppend(l, term, RAFT_COMMAND, buf, NULL);
+ struct raft_entry_local_data loc = (local_data != NULL) ? local_data[i] : (struct raft_entry_local_data){};
+ rv = logAppend(l, term, RAFT_COMMAND, bufs[i], loc, true, NULL);
  if (rv != 0) {
  return rv;
  }
@@ -624,7 +628,7 @@ int logAppendConfiguration(struct raft_log *l,
  }
 
  /* Append the new entry to the log. */
- rv = logAppend(l, term, RAFT_CHANGE, &buf, NULL);
+ rv = logAppend(l, term, RAFT_CHANGE, buf, (struct raft_entry_local_data){}, true, NULL);
  if (rv != 0) {
  goto err_after_encode;
  }

src/raft/log.h

@@ -113,13 +113,16 @@ int logReinstate(struct raft_log *l,
 int logAppend(struct raft_log *l,
  raft_term term,
  unsigned short type,
- const struct raft_buffer *buf,
+ struct raft_buffer buf,
+ struct raft_entry_local_data local_data,
+ bool is_local,
  void *batch);
 
 /* Convenience to append a series of #RAFT_COMMAND entries. */
 int logAppendCommands(struct raft_log *l,
  const raft_term term,
  const struct raft_buffer bufs[],
+ const struct raft_entry_local_data local_data[],
  const unsigned n);
 
 /* Convenience to encode and append a single #RAFT_CHANGE entry. */

src/raft/replication.c

@@ -1235,7 +1235,7 @@ int replicationAppend(struct raft *r,
  goto err_after_request_alloc;
  }
 
- rv = logAppend(r->log, copy.term, copy.type, &copy.buf, NULL);
+ rv = logAppend(r->log, copy.term, copy.type, copy.buf, (struct raft_entry_local_data){}, false, NULL);
  if (rv != 0) {
  goto err_after_request_alloc;
  }

src/raft/start.c

@@ -71,8 +71,8 @@ static int restoreEntries(struct raft *r,
  r->last_stored = start_index - 1;
  for (i = 0; i < n; i++) {
  struct raft_entry *entry = &entries[i];
- rv = logAppend(r->log, entry->term, entry->type, &entry->buf,
- entry->batch);
+ rv = logAppend(r->log, entry->term, entry->type, entry->buf,
+ entry->local_data, entry->is_local, entry->batch);
  if (rv != 0) {
  goto err;
  }

src/raft/uv_append.c

@@ -597,7 +597,7 @@ static size_t uvAppendSize(struct uvAppend *a)
 {
  size_t size = sizeof(uint32_t) * 2; /* CRC checksums */
  unsigned i;
- size += uvSizeofBatchHeader(a->n); /* Batch header */
+ size += uvSizeofBatchHeader(a->n, true); /* Batch header */
  for (i = 0; i < a->n; i++) { /* Entries data */
  size += bytePad64(a->entries[i].buf.len);
  }

src/raft/uv_encoding.c

@@ -86,10 +86,16 @@
  sizeof(uint64_t) /* Last log term. */;
 }
 
-size_t uvSizeofBatchHeader(size_t n)
+size_t uvSizeofBatchHeader(size_t n, bool with_local_data)
 {
- return 8 + /* Number of entries in the batch, little endian */
- 16 * n /* One header per entry */;
+ size_t res = 8 + /* Number of entries in the batch, little endian */
+ 16 * n; /* One header per entry */;
+ if (with_local_data) {
+#ifdef DQLITE_NEXT
+ res += 8; /* Local data length, applies to all entries */
+#endif
+ }
+ return res;
 }
 
 static void encodeRequestVote(const struct raft_request_vote *p, void *buf)
@@ -137,7 +143,7 @@
  bytePut64(&cursor, p->prev_log_term); /* Previous term. */
  bytePut64(&cursor, p->leader_commit); /* Commit index. */
 
- uvEncodeBatchHeader(p->entries, p->n_entries, cursor);
+ uvEncodeBatchHeader(p->entries, p->n_entries, cursor, false /* no local data */);
 }
 
 static void encodeAppendEntriesResult(
@@ -295,14 +301,22 @@
 
 void uvEncodeBatchHeader(const struct raft_entry *entries,
  unsigned n,
- void *buf)
+ void *buf,
+ bool with_local_data)
 {
  unsigned i;
  void *cursor = buf;
 
  /* Number of entries in the batch, little endian */
  bytePut64(&cursor, n);
 
+ if (with_local_data) {
+#ifdef DQLITE_NEXT
+ /* Local data size per entry, little endian */
+ bytePut64(&cursor, (uint64_t)sizeof(struct raft_entry_local_data));
+#endif
+ }
+
  for (i = 0; i < n; i++) {
  const struct raft_entry *entry = &entries[i];
 
@@ -363,7 +377,8 @@
 
 int uvDecodeBatchHeader(const void *batch,
  struct raft_entry **entries,
- unsigned *n)
+ unsigned *n,
+ uint64_t *local_data_size)
 {
  const void *cursor = batch;
  size_t i;
@@ -376,6 +391,17 @@
  return 0;
  }
 
+ if (local_data_size != NULL) {
+#ifdef DQLITE_NEXT
+ uint64_t z = byteGet64(&cursor);
+ if (z == 0 || z > sizeof(struct raft_entry_local_data) || z % sizeof(uint64_t) != 0) {
+ rv = RAFT_MALFORMED;
+ goto err;
+ }
+ *local_data_size = z;
+#endif
+ }
+
  *entries = raft_malloc(*n * sizeof **entries);
 
  if (*entries == NULL) {
@@ -430,7 +456,7 @@
  args->prev_log_term = byteGet64(&cursor);
  args->leader_commit = byteGet64(&cursor);
 
- rv = uvDecodeBatchHeader(cursor, &args->entries, &args->n_entries);
+ rv = uvDecodeBatchHeader(cursor, &args->entries, &args->n_entries, false);
  if (rv != 0) {
  return rv;
  }
@@ -549,33 +575,38 @@
  return rv;
 }
 
-void uvDecodeEntriesBatch(uint8_t *batch,
- size_t offset,
- struct raft_entry *entries,
- unsigned n)
+int uvDecodeEntriesBatch(uint8_t *batch,
+ size_t offset,
+ struct raft_entry *entries,
+ unsigned n,
+ uint64_t local_data_size)
 {
  uint8_t *cursor;
- size_t i;
 
  assert(batch != NULL);
 
  cursor = batch + offset;
 
- for (i = 0; i < n; i++) {
+ for (size_t i = 0; i < n; i++) {
  struct raft_entry *entry = &entries[i];
  entry->batch = batch;
+ entry->buf.base = (entry->buf.len > 0) ? cursor : NULL;
 
- if (entry->buf.len == 0) {
- entry->buf.base = NULL;
- continue;
- }
-
- entry->buf.base = cursor;
-
- cursor = cursor + entry->buf.len;
+ cursor += entry->buf.len;
  if (entry->buf.len % 8 != 0) {
  /* Add padding */
  cursor = cursor + 8 - (entry->buf.len % 8);
  }
+
+ entry->is_local = false;
+
+ entry->local_data = (struct raft_entry_local_data){};
+ assert(local_data_size <= sizeof(entry->local_data.buf));
+ assert(local_data_size % 8 == 0);
+#ifdef DQLITE_NEXT
+ memcpy(entry->local_data.buf, cursor, local_data_size);
+ cursor += local_data_size;
+#endif
  }
+ return 0;
 }